The scr-1 mutant is hypersensitive to zeocin, a DNA damage reagent. A) Wild-type (WS) and scr-1 seedlings 22 d after germination in MS medium. B), C) Wild-type (WS) and scr-1 seedlings 14 d after 8-d-old seedlings were transferred to MS medium containing 20 B) or 50 μg/mL C) zeocin. D) Representative images from the comet assay, showing damaged nuclei in the roots of 8-d-old wild-type and scr-1 seedlings, with or without zeocin treatment (10 µg/mL zeocin for 1 h), before (left) and after (right) processing with the CASP software. The damaged DNA (in the tail) is marked in a different color. E) Statistical analysis of the percentage of DNA in the comet tail using the CASP software. The number below the graph indicates the number of nuclei examined. The median is the middle value of the data set. The upper and lower quartiles are equal to 25% and 75% of all values in the sample in a descending order, respectively. The value in the top whisker is the lower quantile + 1.5 times IRQ, and the value in the bottom whisker is the upper quantile − 1.5 times IRQ. Points represent values for individual samples. Outliers are those with a value greater than Q3 + (1.5 IQR) or less than Q1 − (1.5 IQR). F) Quantitative PCR assay of telomere length. Two days after 6-d-old WS and scr seedlings were transferred to MS medium containing 0, 1, 2, 5, and 10 µg/mL zeocin. Three biological replicates. The values are the mean ± Sd, 3 biological replicates. Tukey's test was used in E) and F). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.